Portable music players such as MP3 players have become very popular. One problem is that the cords going from the music player to the earbuds or headphones can get in the way or become tangled, especially with activities such as jogging.
There are wireless earbuds but they are expensive and limited in functionality. Sennhieser, for example, now offers a system called the MX W1 that retails for about $500 and uses a small transmitter to send modulated audio signals to wireless in-ear receivers. While the system is digital and no doubt offers high quality sound reproduction, the transmitter is somewhat large and the receivers can only be used with that transmitter.